stereo display support

This is likely to be tied to how each graphics drivers implement stereoscopic support.
I don't see how this can be implemented or emulated in the dummy driver in a meaningful way using the software opengl renderer. We could use two virtual dummy screens, but forcing applications to use separate screens for each eye is likely to be very difficult, even with a virtualgl-like interposer.

This may require us to run in desktop mode with multiple X11 screens and forward each one to the client.

Then the client code probably just use a PFD_STEREO context and render each eye with glDrawBuffer(BACK_LEFT) / glDrawBuffer(BACK_RIGHT). See the opengl example in ​NVIDIA 3D VISION PRO AND STEREOSCOPIC 3D. (we don't need to worry about fulcrum and parallax)

13 "Tridelity SL stereo mode, for use with Tridelity SL display devices": unlikely to work

So the only mode that we're likely to be able to forward is (4). Even if some of the other ones could be captured somehow (5, 6, 7, 8, 9), handling the data would be complicated and require extra work for no benefit.

What is used client-side for actually displaying the two views we have captured should not be a concern and we should even be able to use all 3D capable GPUs via the opengl client.